Many different processes may take place at the magnetopause. To distinguish the various mechanisms requires simultaneous multipoing observations in the dayside magnetosphere. Such coincident observations were made by a number of spacecraft located in the solar wind, at the magnetopause, at geosynchronous orbit, and at polar orbit on September 23, 1986. Beginning at 1110 UT, the Bz component of the IMF underwent three periodic cycles, each with a duration of about 7 min, and there were 4 solar wind pressure pulses with a period of 10 min, as recorded by the IMP 8 satellite. The ISEE satellite pair crossed the magnetopause near local noon at 1125 UT and recorded two bipolar events in the normal component of the magnetic field at 1115 and 1120 UT. In addition, ISEE 1 observed a bipolar event at 1118 UT that ISEE 2 did not. Periodic oscillations and compressions of the magnetic field were then subsequently seen at geosynchronous orbit in the dawn sector. Greenland magnetometer stations also located in the morning sector recorded transient responses to the solar wind pressure pulses. The East Coast stations (near local noon) apparently observed a different vortex at 1122 UT. Viking auroral images show an activation of a localized feature poleward of the dayside auroral distribution at 1122 UT. An auroral enhancement, seen at 1128 UT in the afternoon sector, moved eastward at a speed of 5 km s-1 and decayed in intensity by 1141 UT. Clear Pc 5 pulsations were seen equatorward of this activation. Differences in both in situ measurements and ionospheric responses to the two bipolar events lead to the conclusion that the 1118 UT event can be interpreted as being associated with reconnection at the same time that the magnetopause was in motion. ¿ American Geophysical Union 1994